Retinoblastoma Family Gene Mutation Detection And Genetic Counseling

Background:Retinoblastoma(RB) is the most common intraocular malignancy in childhood.The retinoblastoma gene RB1 is located on chromosome 13q14,and known as the first tumor suppressor gene identified.Hereditary form and non-hereditary form of retinoblastoma vary a lot in terms of clinical features,mutation type and management. For hereditary RB,molecular genetic study can identify the patients at risk as early as possible,thus enabling a better prognosis.An extraordinarily broad spectrum of mutations has been determined for RB1 gene,whereas development of molecular biology has provided abundant accesses to a satisfactory detection rate when used in combination.Objective:To establish genetic diagnosis for the RB patients and families collected;to translate the genetic results to the clinical setting for genetic counseling;to update the RB1 mutation spectrum.Method:Mutation analysis was carried out by extraction of genomic DNA from peripheral white blood cell and tumor tissue(if applicable),respectively,amplification of each exon with its flanking introns and promoter region,direct sequencing and comparison with reference sequences.Results:In one case of hereditary RB,a germline mutation of g.39470 G＞T and a somatic mutation of g.2078 ins C were identified,validating the "two hit model".In one case of sporadic bilateral RB,a germline mutation of g.45844 G＞A was identified.The two substitutions were both novel mutations.No germline mutation was identified in another 2 sporadic unilaterally affected cases,but loss of heterozygosity was highly suspected in one of the patients. Conclusion:Direct sequencing was feasible for genetic diagnosis of retinoblastoma,as most mutations could be identified with relatively low costs,and negative results could proceed to other genetic techniques.Genetic diagnosis could be applied for genetic counseling,and close follow-up of carriers might allow early detection of the tumor to preserve eyesight.